The concept of using rail transport for transporting loaded trailers which would otherwise be imoved by road transport is not a new one. There are clear advantages in being able to transport trailers over long distances by train. For example, only one driver may be required to transport as much as 100 loads or more of trailers compared with the corresponding situation on the road where 100 or more drivers would be required. As the trailers can be detached from their prime movers during these rail transporting operations, there is also significant reduction in wear and tear on the prime movers and savings in fuel costs as well.
Furthermore, the fact that the. trailers which are often quite heavy are not travelling along long stretches of roads between capital cities means that road damage between those cities can be substantially reduced. In addition accidents involving heavy vehicles should be reduced.
Because of the obvious advantages of combined road/rail transporting systems, various approaches to achieving such transport have been proposed. For example, in one approach, trailers are driven onto a "basketp" and detached from their prime mover. The baskets are then lifted by crane onto a railway flat car and secured thereto. At the receiving depot, the baskets are again removed by cranes and the trailers are driven off the baskets by a prime mover provided at the depot. Whilst this type of approach is workable, it suffers from the disadvantages that there is a considerable amount of handling involved in locating the trailers in the baskets and moving them by crane onto the individual flat cars of the train. Furthermore, this same amount of handling is duplicated at the receiving depot. In addition, the capital and labour costs associated with this approach all add to the overall cost of transport which can be quite high as a result.
In another approach, railway wagons are aligned over a revolvable vertically movable platform which moves to align wagons with the height of the platform to allow trailers to be driven directly thereon. Again, whilst such an approach does work, it has the limitation that each wagon must be individually located above the moveable rotating platform after being disconnected from the train prior to loading or unloading and must then be rejoined with the train on a wagon by wagon basis. This represents a major limitation which slows the loading and unloading process requiring considerable labour and results in a high overall transport cost.
In yet another approach, individual bogies are constructed so that they are able to support the ends of trailers and hold them above a railway line. Thus the trailers themselves interconnect successive bogies to form a train. The obvious disadvantages with this approach arc that the strength of the train is limited to the strength of the individual trailers. As road transport trailers are generally not as robustly constructed as railway wagons, there is a severe limitation on the length of any train-which can be put together in this fashion as the length of a train is dependent on the weakest link in a train i.e. the weakest trailer. In addition, there are difficulties in connecting up the trailers in this fashion because of the degree of handling involved.
Generally speaking, most approaches are limited in terms of the height of the load a train can carry because of the height restrictions imposed by existing bridges and tunnels under which and through which the train must travel and the limitations a high load center of gravity may present in travelling around bends at speed.
Because of the disadvantages of the various approaches which have been taken to transport road haulage trailers, there is a need for an integrated approach to the problem which involves being able to haul large numbers of trailers on the one train, requires relatively easy handling at both the loading and unloading stages, and is capable of accepting trailers of variable height and centre of gravity.